Circuit breaker having bimetal rigidly secured to cradle



Oct. 6, 1964 J. H. LEONARD 3,152,232

CIRCUIT BREAKER HAVING BIMETAL RIGIDLY SECURED TO CRADLE Filed Feb. 29,1960 3 Sheets-Sheet 1 IN VEN TOR. JHMEJ A. [Ed/V0180 a flJreoLEMc. 546m,6965 gfamm A 77042 ME 70' Oct. 6, 1964 J. H. LEONARD 3,152,232

CIRCUIT BREAKER HAVING BIMETAL RIGIDLY SECURED TO CRADLE Filed Feb. 29,1960 3 Sheets-Sheet 2 IN VEN TOR. qfluar lean/Zea BY 17,404 EA z, Ema6528 f SOFFE/I/ J. H. LEONARD Oct. 6, 1964 CIRCUIT BREAKER HAVINGBIMETAL RIGIDLY SECURED TO CRADLE 3 Sheets-Sheet 3 Filed Feb. 29. 1960INVENTOR. Jfl/WEJ A. 160N660 United States Patent 3,152 232 CIRCUITBREAKER HAVTNG BIMETAL RIGIDLY SECURED T0 CRADLE I James H. Leonard,Clifton Heights, Pa., assignor to I-T-E The instant invention relates tocircuit breakers in general and more particularly to a circuit breakermechanism housed within a narrow casing.

In recent years it has been the practice to construct circuit breakersfor home and light industrial applications with casings whose widths areone inch or multiples thereof.

More recently, the trend has been to supply individual circuit breakerprotection to many circuits even those carrying light loads. Because ofthis, the capacity of existing panelboards, while sufficientelectrically, were not sufficient in physical size to accommodate thegreater numbers of circuit breakers. Further, panelboards having therequisite physical size to accommodate the greater number of circuitbreakers were wasteful of material and space.

Thus, it became necessary to construct circuit breakers having narrowhousing. For example, a typical circuit breaker of 20 amp rating wasusually provided with a molded casing having a one inch width. A circuitbreaker of this rating can be replaced by a circuit breaker whose moldedinsulating housing is one-half inch in width.

Accordingly, it is a primary object of the instant invention to providea narrow molded case circuit breaker which is economical to construct,is reliable in operation and is simple to calibrate.

It has been a problem in circuit breakers of low current rating, say inthe range of to amperes, to generate and confine heat in the currentsensing element or bimetal to elevate the temperature thereof to such apoint that the thermal tripping of the circuit breaker is notsubstantially affected by fluctuations in ambient temperature. In lowrated circuit breakers a large amount of the heat generated in thebimetal escapes through the electrical connections to the bimetal outthrough the connecting conductors. If electrical connections are made tothe bimetal through pressure joints, as opposed to welded braidconnections, the pressure joints will act as thermal barriers confiningheat generated within the bimetal to the bimetal. This will cause thebimetal to operate at an elevated temperature so that normal variationsin ambient temperature appear as a smaller percentage of the temperaturechange required for tripping the circuit breaker.

In the device of the instant invention a pressure joint is formedbetween the movable contact arm and the releasable cradle with contactpressure being established through the tensioning action of the mainoperating spring. Each operation of the circuit breaker between the openand closed position thereof causes awiping action to take place at thepressure point thereby cleaning the joint so that a high electricalresistance is not formed.

Cost is maintained at a minimum without sacrificing reliability ofoperation by eliminating as many elements as possible and also providinga construction wherein many elements perform dual functions.

The instant invention provides a construction wherein the thermal andmagnetic trips are calibrated independently of one another. The magnetictrip is of the low current type while the thermal trip is such that itscaliice 2 bration may be established prior to the mounting thereof inthe circuit breaker case.

inmost prior art circuit breakers a single latching surface is utilizedto retain the releasable cradle. Tripping was initiated either thermallyor magnetically by causing motion of the single latching surface so thatboth thermal and magnetic trips Were interdependent.

In the circuit breaker of the instant invention a latch means isprovided which is comprised of main and intermediate latch members withthe intermediate latch member having one portion thereof utilized as alatch surface for magnetic tripping and another portion utilized as alatch surface for the thermal tripping. The bimetal, or thermal trippingelement, is positioned to deflect out of the plane of movemnet of thereleasable cradle to which the bimetal is affixed while the latchmembers are arranged to pivot around axes perpendicular to thereleasable cradle. Until automatic tripping has actually occurred therelationship between the bimetal and intermediate latch member isunaffected by the position of the main latch member which is movabledirectly through the action of the magnetic tripping device. Similarly,a deflection of the bimetal will in no way affect the relationshipbetween the elements comprising the magnetic trip means.

The absolute independence of the thermal and magnetic'trip deviceresults in the advantage of being able to adjust the tripcharacteristics of the breaker so as to achieve low magnetic trippingwithout utilizing a coil. Further, the thermal tripping characteristicmay be calibrated prior to installing the thermal trip unit into thecircuit breaker case.

The latter is accomplished by providing a sub-assembly comprising areleasable cradle, the bimetal having one end rigidly secured to thecradle and the intermediate latch member pivoted to the cradle andoperatively positioned so as to cooperate with the free end of thebimetal to form the latch for the thermal tripping means.

The circuit breaker of the instant invention includes novel means fordeionizing and directing arcing gases through the case vent opening.This means is comprised of a narrow elongated slit at the bottom of thecase formed by the cooperation of the mating halves comprising the case.The slit forming portions of the mating halves are ofi set so that theslit is not formed as a small opening in the center of a large surfacebut as an opening positioned adjacent to a wall. The wall initially actsto create a turbulence in the arcing gases and thereafter serves todirect the deionized gases through the vent opening.

Thus, it is another object of the instant invention to provide a novelcircuit breaker of narrow construction including a sub-assembly wherebythe thermal tripping characteristic of the breaker may be calibratedexternally thereof.

Still another object is to provide a novel circuit breaker sub-assemblywherein the bimetal element is rigidly secured to a releasable cradlewith the free end of the bimetal movable away from the plane of movementof the cradle.

Still another object is to provide a circuit breaker constructionwherein the contact arm is electrically connected to the circuit througha pressure joint formed by the abutment of the contact arm against thereleasable cradle.

A still further object is to provide improved venting for the arc gasesby utilizing a housing construction wherein an optimum degree ofturbulence is created and at the same time the gases are directed out ofthe circuit breaker case so as to prevent excess back pressures frombeing created.

These as well as other objects of the instant invention shall becomereadily apparent after reading the following description of theaccompanying drawing in which:

FIGURES 1-3 are side elevations of a circuit breaker constructed inaccordance with the instant invention with the cover of the casingremoved to reveal the operating mechanism. In FIGURE 1 the circuitbreaker is in the On position, in FIGURE 2 the circuit breaker is in themanual Off position, and in FIGURE 3 the circuit breaker is in thetripped position.

FIGURE 4 is a side elevation of the cradle sub-assembly.

FIGURES 4A and 4B are cross-sections taken through lines IA-4A and4B-4B, respectively, of FIGURE 4 looking in the directions of therespective arrows.

FIGURE 5 is an exploded perspective view of the circuit breakermechanism.

FIGURE 6 is a fragmentary cross-section of the breaker housing takenthrough line 66 of FIGURE 1 looking in the direction of arrows 66.

Now referring to the figures, circuit breaker includes a housingcomprised of a case 21 and cover 22 mated to each other along line 23and secured by rivets 23a. The current path through circuit breaker 20comprises line terminal 24, conducting strap 25, stationary contact 26,movable contact 27, contact arm 28, the pressure joint 29 at the upperend of contact arm 28, releasable cradle 30, bimetal 31, conductingbraid 32 and load terminal contact member 33.

Spring 79 acts as a gripping means for a load conductor (not shown)which passes through case opening '78 into engagement with load contact33. Adapter means '77, of a type fully described in my copendingapplication Serial No. 18,411, filed March 29, 1960, entitled PanelboardAdapter, and assigned to the assignee of the in stant invention isutilized to electrically connect line terminal 24 to a panelboard busbar (not shown).

Circuit break 20 includes an operating member 34 having an extension orhandle 35 which extends upwardly through an opening 36 in the top ofhousing 21, 22 to provide a manual operating handle. Operating member 34is also provided with an arcuate portion 37 extending in the directionof movement of handle 35 and disposed within arcuate groove 38 of case21 and a similar groove in cover 22. The upper end of handle arm 39extends into suitable recesses of operating member 34 while the lowerend of arm 39 abuts a rounded internal formation of case 21 to form apivot 40 for operating member 34-.

Main operating spring 41 is secured at one end 42 thereof to arm 39where the bifurcated end thereof engages member 34 while the other end43 of spring 41 is connected to movable contact arm 28. Spring 41 is atension spring comprised of an open loop with elongated arms extendingin opposite directions. The tension force exerted by spring 41 urges theupper end of contact arm 23 to abut cradle 39 at joint 29.

With subassembly 1% (FIGURE 5) in the latched position of FIGURES 1 and2, circuit breaker 20 may be operated manually between the On and Offpositions. When handle 35 is moved to the right with respect to FIGURE 1at such time as the spring end at 42 passes to the right of a linejoining spring end 43 and joint 23, the line of action of spring 41 willbe so positioned so as to effect a snap opening of contacts 26, 27 bypivoting contact arm 28 in a counterclockwise direction about joint 29to the Off position of FIGURE 2. The reverse action takes place ashandle 35 is moved to the left with respect to FIGURE 2. During thisoperation, at such time as the line of action of spring 41 extendingbetween spring ends 42, 43 passes to the left of the line joining springend 43 and joint 29 in FIGURE 2, contact arm 28 will be snapped in aclockwise direction about joint 29 to the closed position of FIGURE 1.

Sub-assembly 1% comprises cradle 30 which is a generally V-shaped memberhaving an opening 44 near the apex thereof which receives a caseembossment 45 serving as a pivot for sub-assembly 180. Bimetal 31, whichforms a part of sub-assembly 100, is fixedly secured at one end 46thereof as by welding to cradle leg 47 in the region of aperture 44.Sub-assembly 100 further includes intermediate latch member 48 pivotallysecured by rivet 49 to cradle 30 at the free end portion 30a of cradleleg 50. The free end portion 30:: of leg 50 as well as tab are embossedformations offset from the general plane of cradle 30. In formingportion 30a stop formation 71 is also formed. Stop 71 cooperates withthe notch 72 in latch member 48 to limit movement of latch 48 about itspivot 49.

Tab 70 is raised above one surface of cradle 30 while disk 73 is weldedto the other surface of cradle 30. Thus, tab 70 and disk 73 areoperatively positioned and spaced from one another to form means (FIGURE4B) which receives the upper end of contact arm 28 in the region ofjoint 29 to provide guidance for arm 28 as it moves between thepositions of FIGURES 1-3.

In order to insure a uniform latch bite between bimetal tip 31a andintermediate latch member 48 a spring in the form of star washer 89(FIGURE 4B) is mounted to rivet 49. Spring 89 urges latch member 48axially along rivet 49 to establish the same latch bite for successiveresettings after thermal tripping. The large round tripped head 88 ofrivet 49 serves to align sub-assembly 100 with respect to the internalWalls of housing 21, 22.

Since contact arm 28 abuts cradle 30 at joint 29 to the right ofembossment 45, the force exerted by main operating spring 41 acts torotate sub-assembly 100 counterclockwise about pivot 45. However,subassembly 100 is restrained against movement in a counterclockwisedirection through the engagement of intermediate latch member 48 withmain latch member 51. Main latch member 51 is comprised of springmaterial and includes a portion of reduced area which extends over theback of magnet 52 so as to form a pivot at 53 for armature 54 which issecured to main latch member 51 by rivet 55.

Magnet 52 is of generally U-shaped cross-section with braid 32 passingbetween the arms of the U to form the energizing turn therefor. Thebiasing action of the spring material forming main latch member 51 urgesarmature 54 in a clockwise direction about its pivot 53 away from magnet52. The lower end of armature 54 abuts a case formation 56 to establishthe air gap between armature 54 and magnet 52 and also establishes thelatching position for member 51. Magnetic tripping takes place when apredetermined magnitude of current flows through braid 32 causing magnet52 to generate flux which attracts armature 54 counterclockwise aboutpivot 53. This rnoves main latch member 51 to the right with respect toFIG- URE 1 so that sub-assembly 100 is no longer restrained. Thus,sub-assembly 100 under the influence of main operating spring 41 rotatesin a counterclockwise direction about pivot 45. When pivot 29 moves tothe left of the line of action of spring 41 in its position of FIGURE 1,spring 41 will urge contact arm 28 in a counterclockwise direction aboutpivot 29 to bring about a snap opening of contacts 26, 27.

The circuit breaker elements are now in the tripped position of FIGURE 3with sub-assembly 100 being positioned by the abutment of handle armextension 60 and cradle surface 61 while offset of contact arm 28 abutscover formation 76.

After magnetic tripping resetting is accomplished by moving operatinghandle 35 to the extreme right position from the intermediate trippedposition of FIGURE 3. During this movement handle arm extension 61)engages cradle 31) along surface 61 so that subassembly is movedclockwise against the force of spring 41 to the latched position ofFIGURE 2. As latch member 48 moves past latched member 51 the roundedportion 63 of intermediate latch member 48 cams latch 51 to the rightuntil latch surface 64 of main latch member 51.

Time delay tripping is accomplished by a deflection of the free end ofbimetal 31 out of the plane of movement of cradle 30. When thisdeflection is suificient to free bimetal offset 31a from intermediatelatch 48 the action of tension spring 41 will rotate cradle in acounterclockwise direction about pivot 45. Initially intermediate latchmember 48 is retained by main latch member 51 so that there is relativemovement between cradle 30 and intermediate latch member 48 about pivot49. As the distance between pivot 49 and main latch member 51 passesbelow the lower end increases, a point is reached where intermediatelatch member 48 is free of main latch member 51 and the subassembly 100moves to the tripped position of FIGURE 3.

Resetting after thermal tripping is accomplished by moving handlefromthe intermediate trip position of FIGURE 3 to the extreme rightposition of FIGURE 2. At the latter portion of this movementintermediate latch member 48 engages case embossment 65 which forcesintermediate latch member 48 in a counterclockwise direction aboutitspivot 49 to a point where member 48 is free of the edge of bimetalextension 31a and at this time the free end of bimetal 31 moves towardthe plane of movement of cradle 30 into latching position.

It is to be noted that as the latch bite between bimetal offset 31a andmember 48 changes due to a deflection of bimetal 31 the latch bitebetween surface 64 and member 51 is not alfected. Similarly, a change inthe magnetic latch bite 64, 51 in no-way effects the thermal latch bite31a, 48. Thus, the thermal and magnetic trips are operated independentlyof one another.

Cover 22 is mated with case 21 to form housing chamber 80, wherein theoperating mechanism is disposed, also forms vent opening 81 (FIGURE 6)which extends for distance X (FIGURE 1) along the bottom of housing 21,

22 Vent 81 is greatly elongated being very narrow in width, say .020".It is to be noted that the cover surface 82 forming vent 81 extendsbeyond the case surface 83 forming vent 81. Thus, gases formed duringcircuit interruption in rushing toward vent 81 initially experienceturbulence within chamber 81 since vent 81 is so narrow. After the gasesare substantially deionized the upper portion of surface 82 notconfronted by surface 83 acts to direct the deionized gases through vent81 out of housing 21, 22.

Thus, I have provided a novel circuit breaker mechanism which isespecially adapted for narrow housings.

Although I have here described preferred embodiment of my novelinvention, many variations and modifications will now be apparent tothose skilled in the art, and I therefore prefer to be limited, not bythe specific disclosure herein, but only by the appending claims.

I claim: i

1. A circuit breaker comprising a pair of cooperating contacts and anoperating mechanism for operating said contacts into and out ofengagement; said mechanism including a releasable cradle, latch meansfor restraining said cradle in a reset position, an operating springurging said cradle to a tripped position, and a manually operable memberfor operating said contacts into and out of engagenrent; said mechanismfurther including a thermal tripping element having a free endoperatively positioned for engagement with said latch means and whendeflected sufficiently to disengage said latch means permitting saidspring to move said cradle to its said trip position wherein saidcontacts are disengaged; said thermal tripping element having anotherend fixedly secured to said cradle; said free end being positioned todeflect away from the plane of movement of said cradle upon heating ofsaid thermal tripping element; said latch means comprising a firstmember pivotally mounted to said cradle to an axis extendingperpendicular to the plane of movement of said cradle; biasing meansurging said first member in the direction of its axis.

2. A circuit breaker comprising a pair of cooperating contacts and anoperating mechanism for operating said contacts into and out ofengagement; said mechanism including a releasable cradle, latch meansfor restraining said cradle in a reset position, an operating springurging said cradle to a tripped position, and a manually operable memberfor operating said contacts into and out of engagement; said mechanismfurther including a thermal tripping element having a free endoperatively positioned for engagement with said latch means and whendeflected sufliciently to disengage said latch means permitting saidspring to move said cradle to its said trip position wherein saidcontacts are disengaged;

said thermal tripping element having another end fixedly secured to saidcradle; said free end being positioned to deflect away from the plane ofmovement of said cradle upon heating of said thermal tripping element; amovable contact arm carrying at one end thereof one of said cooperatingcontacts and at the other end thereof being mounted to said cradle toform a pivotal connection therewith for movement relative to saidcradle.

3. A circuit breaker comprising a pair of cooperating contacts and anoperating mechanism for operating said contacts into and out'ofengagement; said mechanism including a releasable cradle, latch meansfor restraining said cradle in a reset position, an operating springurging said cradle to a tripped position, and a manually operable memberfor operating said contacts into and out of engagement; said mechanismfurther including a thermal tripping element having a free endoperatively positioned for engagement with said latch means and whendeflected sufliciently to disengage said latch means permitting saidspring to move said cradle to its said trip position wherein saidcontacts are disengaged; said thermal tripping element having anotherend fixedly secured to said cradle; said free end being positioned todeflect away from the plane of movement of said cradle upon heating ofsaid thermal tripping element; a movable contact arm carrying at one endthereof one of said cooperating contacts and at the other end thereofbeing mounted to said cradle to form a pivotal connection therewith;said pivotal connection comprising a portion of the sole electrical pathbetween said contact arm and said thermal tripping element.

4. A circuit breaker comprising a pair of cooperating contacts and anoperating mechanism for operating said contacts into and out ofengagement; said mechanism including a releasable cradle, latch meansfor restraining said cradle in a reset position, an operating springurging said cradle to a tripped position, and a manually operable memberfor operating said contacts into and out of engagement; said mechanismfurther including a thermal tripping element having a free endoperatively positioned for engagement with said latch means and whendeflected sufliciently to disengage said latch means permitting saidspring to move said cradle to its said trip position wherein saidcontacts are disengaged; said thermal tripping element having anotherend fixedly secured to said cradle; said free end being positioned todeflect away from the plane of movement of said cradle upon heating ofsaid thermal tripping element; a movable contact arm carrying at one endthereof one of said cooperating contacts and at the other end thereofbeing mounted to said cradle at a pivotal connec tion; said operatingspring comprising a tension producing member connected between saidmanually operable member and said contact arm; and in tensioncorresponding to said contacts being in their engaged position.

5. A circuit breaker comprising a pair of cooperating contacts and anoperating mechanism for operating said contacts into and out ofengagement; said mechanism including a releasable cradle, latch meansfor restraining said cradle in a reset position, an operating springurging said cradle to a tripped position, and a manually operable memberfor operating said contacts into and out of engagement; said mechanismfurther including a thermal tripping element having a free endoperatively positioned for engagement with said latch means and whendeflected sufliciently to disengage said latch means permitting saidspring to move said cradle to its said trip position wherein saidcontacts are disengaged; said thermal tripping element having anotherend fixedly secured to said cradle; said free end being positioned todeflect away from the plane of movement of said cradle upon heating ofsaid thermal tripping element; a movable contact arm carrying at one endthereof one of said cooperating contacts and at the other end thereofbeing mounted to said cradle at a pivotal connection; said operatingspring comprising a tension producing member connected between saidmanually operable member and said contact arm; and in tensioncorresponding to said contacts being in their engaged position; saidtension producing member comprising a single open ended loop having armsextending in opposite directions.

6. A circuit breaker comprising a pair of cooperating contacts and anoperating mechanism for operating said contacts into and out ofengagement; said mechanism including a releasable cradle, latch meansfor restraining said cradle in a reset position, an operating springurging said cradle to a tripped position, and a manually operable memberfor operating said contacts into and out of engagement; said mechanismfurther including a thermal tripping element having a free endoperatively positioned for engagement with said latch means and Whendeflected sufliciently to disengage said latch means permitting saidspring to move said cradle to its said trip position wherein saidcontacts are disengaged; said thermal tripping element having anotherend fixedly secured to said cradle; said free end being positioned todeflect away from the plane of movement of said cradle upon heating ofsaid thermal tripping element; said latch means comprising a firstmember pivotally mounted to said cradle to an axis extendingperpendicular to the plane of movement of said cradle and a secondmember for restraining movement of said first member; said mechanismalso including an instantaneous trip means for moving said second memberfor release thereby of said first member with release of said firstmember by said second member permitting said spring to move said cradleto its said trip position.

7. A circuit breaker comprising a pair of cooperating contacts and anoperating mechanism for operating said contacts into and out ofengagement; said mechanism including a releasable cradle, latch meansfor restraining said cradle in a reset position, an operating springurging said cradle to a tripped position, and a manually operable memberfor operating said contacts into and out of engagement; said mechanismfurther including a thermal tripping element having a free endoperatively positioned for engagement with said latch means and Whendeflected sufiiciently to disengage said latch means permitting saidspring to move said cradle to its said trip position wherein saidcontacts are disengaged; said thermal tripping element having anotherend fixedly secured to said cradle; said free end being positioned todeflect away from the plane of movement of said cradle upon heating ofsaid thermal tripping element; said latch means comprising a firstmember pivotally mounted to said cradle to an axis extendingperpendicular to the plane of movement of said cradle and a secondmember for restraining movement of said first member; said mechanismalso including an instantaneous trip means for moving said second memberfor release thereby of said first member with release of said firstmember by said second member permitting said spring to move said cradleto its said trip position; said second member being pivotally mountedabout an axis perpendicular to the plane of movement of said cradle.

8. A circuit breaker comprising a pair of cooperating contacts and anoperating mechanism for operating said contacts into and out ofengagement; said mechanism including a releasable cradle, latch meansfor restraining said cradle in a reset position, an operating springurging said cradle to a tripped position, and a manually operable memberfor operating said contacts into and out of engagement; said mechanismfurther including a thermal tripping element having a free endoperatively positioned for engagement with said latch means and whendeflected sufliciently to disengage said latch means permitting saidspring to move said cradle to its said trip position wherein saidcontacts are disengaged; said thermal tripping element having anotherend fixedly secured to said cradle; said free end being positioned todeflect away from the plane of movement of said cradle upon heating ofsaid thermal tripping element; said latch means comprising a firstmember pivotally mounted to said cradle to an axis extendingperpendicular to the plane of movement of said cradle and a secondmember for restraining movement of said first member; said mechanismalso including an instantaneous trip means for moving said second memberfor release thereby of said first member with release of said firstmember by said second member permitting said spring to move said cradleto its said trip position; said second member being pivotally mountedabout an axis perpendicular to the plane of movement of said cradle; amovable contact arm carrying at one end thereof one of said cooperatingcontacts and at the other end thereof being mounted to said cradle at apivotal connection.

9. A circuit breaker comprising a pair of cooperating contacts and anoperating mechanism for operating said contacts into and out ofengagement; said mechanism including a releasable cradle, latch meansfor restraining said cradle in a reset position, an operating springurging said cradle to a tripped position, and a manually operable memberfor operating said contacts into and out of engagement; said mechanismfurther including a thermal tripping element having a free endoperatively positioned for engagement with said latch means and whendeflected suificiently to disengage said latch means permitting saidspring to move said cradle to its said trip position wherein saidcontacts are disengaged; said thermal tripping element having anotherend fixedly secured to said cradle; said free end being positioned todeflect away from the plane of movement of said cradle upon heating ofsaid thermal tripping element; said latch means comprising a firstmember pivotally mounted to said cradle to an axis extendingperpendicular to the plane of movement of said cradle and a secondmember for restraining movement of said first member; said mechanismalso including an instantaneous trip means for moving said second memberfor release thereby of said first member with release of said firstmember by said second member permitting said spring to move said cradleto its said trip position; said second member being pivotally mountedabout an axis perpendicular to the plane of movement of said cradle; amovable contact arm carrying at one end thereof one of said cooperatingcontacts and at the other end thereof being mounted to said cradle at apivotal connection; said operating spring comprising a tension producingmember connected between said manually operable member and said contactarm.

10. A circuit breaker comprising a pair of cooperating contacts and anoperating mechanism for operating said contacts into and out ofengagement; said mechanism including a releasable cradle, latch meansfor restraining said cradle in a reset position, an operating springurging said cradle to a tripped position, and a manually operable memberfor operating said contacts into and out of engagement; said mechanismfurther including a thermal tripping element having a free endoperatively positioned for engagement with said latch means and whendeflected sufl'iciently to disengage said latch means permitting saidspring to move said cradle to its said trip position wherein saidcontacts are disengaged; said thermal tripping element having anotherend fixedly secured to said cradle; said free end being positioned todeflect away from the plane of movement of said cradle upon heating ofsaid thermal tripping element; said latch means comprising a firstmember pivotally mounted to said cradle to an axis extendingperpendicular to the plane of movement of said cradle and a secondmember for restraining movement of said first member; said mech anismalso including an instantaneous trip means for moving said second memberfor release thereby of said first member with release of said firstmember by said second member permitting said spring to move said cradleto its said trip position; said instantaneous trip means comprising amagnet and cooperating armature; biasing means urging said second memberto latching position wherein said second member is engageable with saidfirst member; movement of said armature toward said magnet beingeffective to move said second member away from said latching position torelease said first member.

11. A circuit breaker comprising a pair of cooperating contacts and anoperating mechanism for operating said contacts into and out ofengagement; said mechanism including a releasable cradle, latch meansfor restraining said cradle in a reset position, an operating springurging said cradle to a tripped position, and a manually operable memberfor operating said contacts into and out of engagement; said mechanismfurther including a thermal tripping element having a free endoperatively positioned for engagement with said latch means and whendeflected sufliciently to disengage said latch means permitting saidspring to move said cradle to its said trip position wherein saidcontacts are disengaged; said thermal tripping element having anotherend fixedly secured to said cradle; said free end being positioned todeflect away from the plane of movement of said cradle upon heating ofsaid thermal tripping element; said latch means comprising a firstmember pivotally mounted to said cradle to an axis extendingperpendicular to the plane of movement of said cradle and a secondmember for restraining movement of said first member; said mechanismalso including an instantaneous trip means for moving said second memberfor release thereby of said first member with release of said firstmember by said second member permitting said spring to move said cradleto its said trip position; said instantaneous trip means comprising amagnet and cooperating armature; biasing means urging said second memberto latching position wherein said second member is engageable with saidfirst member; movement of said armature toward said magnet beingeffective to move said second member away from said latching position torelease said first member; a movable contact arm carrying at one endthereof one of said cooperating contacts and at the other end thereofbeing mounted to said cradle at a pivotal connection; said operatingspring comprising a tension producing member connected between saidmanually operable member and said contact arm.

12. A circuit breaker comprising a pair of cooperating contacts and anoperating mechanism for operating said contacts into and out ofengagement; said mechanism including a releasable cradle, latch meansfor restraining said cradle in a reset position, an operating springurging said cradle to a tripped position, and a manually operable memberfor operating said contacts into and out of engagement; said mechanismfurther including a thermal tripping element having a free endoperatively positioned for engagement with said latch means and whendeflected suiiiciently to disengage said latch means permitting saidspring to move said cradle to its said trip position wherein saidcontacts are disengaged; said thermal tripping element having anotherend fixedly secured to said cradle; said free end being positioned todeflect away from the plane of movement of said cradle upon heating ofsaid thermal tripping element; a movable contact arm carrying at one endthereof one of said cooperating contacts and at the other end thereofbeing mounted to said cradle to form a pivotal connection therewith formovement rela tive to said cradle.

References Cited in the file of this patent UNITED STATES PATENTS2,025,872 Laganke Dec. 31, 1935 2,166,555 Rowe -Iuly 18, 1939 2,222,312Green Nov. 19, 1940 2,288,081 Frank June 30, 1942 2,406,325 Dorfman Aug.27, 1946 2,653,202 Cole Sept. 22, 1953 2,661,414 Casey Dec. 1, 19532,719,203 Gelzheiser et al. Sept. 27, 1955 2,811,606 Norden Oct. 29,1957 2,898,427 Nadeau Aug. 4, 1959

2. A CIRCUIT BREAKER COMPRISING A PAIR OF COOPERATING CONTACTS AND ANOPERATING MECHANISM FOR OPERATING SAID CONTACTS INTO AND OUT OFENGAGEMENT; SAID MECHANISM INCLUDING A RELEASABLE CRADLE, LATCH MEANSFOR RESTRAINING SAID CRADLE IN A RESET POSITION, AN OPERATING SPRINGURGING SAID CRADLE TO A TRIPPED POSITION, AND A MANUALLY OPERABLE MEMBERFOR OPERATING SAID CONTACTS INTO AND OUT OF ENGAGEMENT; SAID MECHANISMFURTHER INCLUDING A THERMAL TRIPPING ELEMENT HAVING A FREE ENDOPERATIVELY POSITIONED FOR ENGAGEMENT WITH SAID LATCH MEANS AND WHENDEFLECTED SUFFICIENTLY TO DISENGAGE SAID LATCH MEANS PERMITTING SAIDSPRING TO MOVE SAID CRADLE TO ITS SAID TRIP POSITION WHEREIN SAIDCONTACTS ARE DISENGAGED; SAID THERMAL TRIPPING ELEMENT HAVING ANOTHEREND FIXEDLY SECURED TO SAID CRADLE; SAID FREE END BEING POSITIONED TODEFLECT AWAY FROM THE PLANE OF MOVEMENT OF SAID CRADLE UPON HEATING OFSAID THERMAL TRIPPING ELEMENT; A MOVABLE CONTACT ARM CARRYING AT ONE ENDTHEREOF ONE OF SAID COOPERATING CONTACTS AND AT THE OTHER END THEREOFBEING MOUNTED TO SAID CRADLE TO FORM A PIVOTAL CONNECTION THEREWITH FORMOVEMENT RELATIVE TO SAID CRADLE.